The present invention is directed to an automotive working machine for the treatment of roadways.
Such working machines are used for the treatment of road material, e.g., for stabilization of ground having insufficient bearing properties, the fragmentation of hard asphalt surfacing, and for the recycling of bound or non-bound road surfaces.
Known machines of the above type are characterized by usually one working drum rotating in a working chamber and being arranged to have its height and inclination adjusted in conformity with the surface to be treated.
The required processes, e.g. the breaking and fragmenting of the milled-off road material, the adding of binding agents, the mixing and distributing of added materials and the like, will take place in said working chamber.
The inventive working process can also be divided into a counter-rotational working process and a co-rotational working process, depending on whether--with the same rotational direction--the peripheral force of the working drum will act against the driving force of the machine or will support it. Because of their relatively wide range of applications, especially in working processes wherein binding agents such as lime or cement are mixed partly in loose form with the surface layer to be treated, such machine are often provided with a closed driver's cabin so as to comply with working safety requirements.
The above described working machines for the refurbishing of roadways comprise a working drum driven either on one or both sides, and a very high drive power may be required depending on the respective application, with the rotational speed of the working drum being adjustable. Since the working process is often performed in the immediate vicinity of lateral obstacles, e.g. embankments, curbs, trees, house walls and so on, difficulties often occur because the slightest possible distance has to be kept between the outer cutting edge of the working drum and the outer edge of the machine in the working range.
The working chamber, extending between the working drum and the outer cover, is of special importance for the result of the working process. The work achieved could be improved, e.g., by an enlarged working chamber having a larger working depth. In known machines, the positions of the working drum axis relative to the drive carriage axes are quite different. Extensive research has revealed that the position of the working drum axis relative to the drive carriage axis is of particular relevance for the detachment behavior. The working machines, usually provided with two drive carriage axes, require considerable pressing forces to obtain the detachment behavior of the working drum, the maximum possible pressing force being determined by the weight of the machine. The arrangement of the working drum is favorable when, if feasible, the whole machine weight can be used in counter-rotational and co-rotational working processes for generating the possibly required pressing forces of the working drum. The outer cover is fixedly arranged on the machine frame. The fixed arrangement is usually advantageous because of its low constructional expenditure (no necessity for guide elements). For the working result, the particle size and resp. the particle distribution of the detached and resp. also picked-up material is of eminent importance. The distribution of the particle sizes is decisively influenced by the geometrical configuration of the working chamber which is determined by defined geometrical relationships between the working drum and the outer cover. Particularly an outer cover which is resistant to mechanical stresses will provide advantageous working results.
The driver's platform, which for safety reasons is imperative in machines of the above type, poses problems due to the resultant increased height of the machine, which is disadvantageous especially during transport of the machine. For this reason, the driver's platform of the known embodiments has been arranged at the rear or the front of the machine which still offer enough space. This, in turn, entails the disadvantage that only one working direction can be visually observed to a really satisfactory extent.
Depending on the nature of the surface to be treated, the working process requires that the working drum axis be adapted with respect to the working depth, i.e. with respect to the relative vertical distance of the working drum axis for the to-be-treated surface and the absolute transverse inclination of the working drum axis. The tools arranged on the periphery of the working drum for performing the material detachment process are partly equipped with cutting tools known from road milling machines.
Depending on their respective type, the presently known methods and devices for the above described working process suffer from one or several of the following disadvantages:
The present solutions for the working drum drive, due to their hydraulic, hydraulic-mechanical or indirectly mechanical concepts, suffer from an unsatisfactory efficiency and corresponding energy losses. A direct mechanical drive has not yet been realized in the above machines.
Although an enlargement of the working space with increased working depth, offering favorable working results, has been realized in some embodiments of working machines, this has been accomplished only at the expense of the advantageous arrangement of the working drum axis relative to the drive carriage axes. This applies also to embodiments wherein, although the working drum axis is arranged between the drive carriage axes, the weight distribution (rear and resp. front axes) is so unfavorable that the above described advantage of using the machine weight for the pressing forces of the working drum cannot be utilized for the counter-rotational working process and the co-rotational working process. On the other hand, embodiments of working machines exist wherein the working drum axis is arranged in a favorable position relative to the drive carriage axes, but these machines do not offer the advantage of an enlargement of the working space with increased working depth.
In present embodiments of working machines, the outer cover is either fixedly or movably arranged on the supporting frame of the machine. In known working machines, the above described advantages of a fixed arrangement are only achieved if the working chamber is non-adjustable. Further, only in case of a fixed arrangement of the working drum housing, so-called breaker bars can be realized, since the fragmentation of material normally produces forces which advantageously are introduced into the machine frame. Adjustable breaker bars, i.e. devices wherein the distance between the breaker bar and the working drum during the working process can be changed, have not yet been realized.
In known working machines, the positioning of the driver's platform has not been satisfactory. Either, with a non-central arrangement, it is not possible to visually monitor the whole machine, or, with a central arrangement of the driver's platform and particularly in case of an embodiment comprising a driver's cabin, the transport height is so large that the transport from one construction site to another one requires a demounting of constructional components.
In the machines known up to now, the indication of the working depth is performed by reference to the relative position between the working drum axis and the drive carriage axis. For this reason, the largevolumed tires, which are frequently used in this type of working machines, will due to their resilient properties inevitably cause a measuring and indication error with respect to the working depth. The use of control devices for the adjustment and maintenance of a preselected working depth has not been realized yet.
Because of the partly high detachment resistance of the material to be worked on, incidents like e.g. the breakage of a cutting tool will cause damage to the holder or other constructional components fixedly attached to the working drum, which due to the resulting repair work will result in considerable operational disturbances and interruptions of the working process. The use of an exchange holder system which is known for so-called road milling machines, has not been considered yet for working machines of the type discussed here.
The above outlined state of the art is described, for instance, in the U.S. Pat. Nos. 5,259,692, 5,190,398 and 5,354,147.